1. Field of the Invention
The present invention relates to methods and devices utilized in a wireless communication system, and more particularly, to methods and devices utilized in the wireless communication system for controlling selection for home cells.
2. Description of the Prior Art
A System Architecture Evolution (SAE) system, set forth by 3GPP (3rd Generation Partnership Project) is a packet core network architecture for UMTS (Universal Mobile Telecommunications System), addressing cost-efficient deployment and operations for mass-market usage of IP services. The main network evolutions include meeting the targets for a radio-interface of a long term evolution (LTE) system, simplified network architecture, an All-IP Network, only packet switched means for all services, no circuit switching, and support for mobility and service continuity between heterogeneous access networks, such as between 2G/3G, LTE, non-3GPP access systems.
The SAE core network, or an evolved packet system (EPS) core network, includes an MME (Mobility Management Entity), an S-GW (Serving Gateway) and a P-GW (PDN gateway). The MME is a control plane entity that manages the attachment to the network, the authentication of the user equipment (UE), and interfaces an E-RAN (evolved radio access network) for the creation of relevant radio bearers. The S-GW is a user plane entity handling packet forwarding uplink and downlink between the PDN gateway and the radio environment (e.g. E-RAN). The S-GW is always located in the network where the UE is camping.
Functions of the SAE include the Non-Access-Stratum (NAS) functions to be performed by the UE in idle mode, the NAS signalling procedures between the UE and an evolved packet core network (EPC) via an E-UTRAN (evolved UMTS radio access network) including eNBs (evolved Node-Bs), and layer 3 signalling procedures between the UE and the EPC via non-3GPP access networks.
Under NAS functions, home cell deployments are defined as a single eNB used in a building or a small group of cells, e.g. in a campus deployment. Access to home cells is restricted to particular subscribers. In home cell deployments, a CSG (closed subscriber group) cell as part of the PLMN (public land mobile network) is only suitable for a UE if an id of the CSG cell is in a whitelist of the UE. The whitelist is a list of CSG cell ids where the UE is allowed to camp.
In the home cell deployments, a CSG area is defined as a tracking area (TA) that consists of a cell or group of cells to which access is restricted to a defined group of users. An eNB, which belongs to a CSG area, sends the CSG cell area identity to the MME whenever authorization needs to be checked in the MME.
A private node-B usually owned by an individual is normally deployed in the home network to provide services for CSG subscribers. In provision of CSG business, a user attempting to be a CSG subscriber goes to an operator's store to subscribe the CSG services and thereby gets a private node-B. The user can use the private node B at home via Internet. The private node-B is set to communicate to the operator's EPS core network via IP connection. The private node B and the EPS core network (i.e. the MME or the Serving Gateway) authorize each other.
However, the user possibly takes the private node B out of the home network coverage, and the prior art does not specify how the private node-B and the EPS deal with this situation. AS a result, the private node B used in unauthorized area works in the same way as in home network coverage. In this situation, the private node-B may use a frequency band that belongs to other operators for data transmission. This is an illegal usage and makes interference to frequency bands licensed for other operators.